I visited my step daughter & son-in-law over the Christmas period, down in London. On the Tuesday (28.12.10) my son-in-law and I went out for a bike ride. He's a lot younger and fitter than me. He took me on a lovely route around the Surrey area, taking in Box Hill and Epsom etc. Anyway, it was a steady pace (for my benefit), and I found it reasonably easy compared to the kind of terrain wher I live (derbyshire), clocking in my first 40 miler. I was really pleased with myself as I've not been out too much lately due to the weather etc. The problem was that I had a banging headache for 2 days after!!. I kept myself well hydrated during the ride and even had an energy gel. After the ride I had plenty of water to drink, but I just couldn't shake the headache. I suppose it could've been due to a bit of over indulgence during the xmas period, plus too little sleep (shift worker!). Any other ideas?, I don't want this kind of thing happening every time I push myself a bit further.